Low reflected-sound-pressure-level, low moisture-vapor-transmission-rate flooring system

ABSTRACT

A flooring system having a top floor layer, a sub-floor, and an underlayment material disposed between the sub-floor and the top floor layer is disclosed. The underlayment material may include a cross-linked, polyolefin foam having a moisture vapor transmission rate of less than about 3.0 lb/1000 ft 2 /24 hr, and an average sound pressure level of less than about 15 dB over a range of about 300 Hz to about 1000 Hz. Foam density, gel fraction, and resin blend may combine to provide an underlayment material having such reflective sound and moisture vapor barrier properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/246,235, filed Sep. 27, 2011, which is a continuation of U.S. patentapplication Ser. No. 11/261,977, filed Oct. 28, 2005, which claimsbenefit under 35 U.S.C. §119(e) of provisional U.S. patent applicationno. 60/622,764, filed Oct. 28, 2004, the disclosures of which areincorporated herein in their entireties.

BACKGROUND OF THE INVENTION

A typical hardwood, laminate, or engineered flooring system may includetwo or more layers. A top layer typically details the pattern andtexture of the product, and may include a protective layer, such as ahard coating, for durability. A core layer may be prepared from pressedfiberboard, for example, or from other suitable materials. A bottomlayer may be included to stabilize the product and to protect it fromdeleterious effects of moisture. Frequently, laminate or engineeredflooring systems employ some type of tongue and groove design to allowthe pieces of the flooring to bond together without requiring the use ofadhesive.

It is well-known that moisture may cause undesirable cupping or warpingof the flooring system. A vapor barrier may be employed to protect thelaminate or engineered flooring system from damage caused by moisture.Though a vapor barrier may provide some protection against moisturedamage, vapor barriers tend to increase the cost and installationcomplexity of such flooring systems.

Another issue that may be experienced with flooring systems is the soundthat may be produced when the floor is used. In multi-story structures,for example, sound created by use of an upper unit floor may betransmitted down into the unit below. Likewise, sound may be reflectedback into the unit in which it is created. A sound barrier layer may beemployed to reduce one or both of transmitted and reflected noise.Typical sound barrier layers include dense rubber and plastic sheets,corks, recycled fibers, and various types of foams. Such sound barriers,however, tend to be heavy and to add to the complexity and overall costof installation.

Examples of conventional foams used in flooring applications have EPCcontents, densities, and gel fraction that, in combination, result incompressive strengths below about 0.50 kg/cm². These properties ofconventional olefin foam underlayments combine to produce relativelyhigh reflected sound pressure levels (i.e., greater than about 13.5 dBaverage) in the 300 Hz to 1000 Hz range. Other underlayment materials,such as fiber pad, cork, and non-cross-linked foam, for example, alsotend to produce relatively high reflected sound pressure levels in the300 Hz to 1000 Hz frequency range. Such materials also tend to producehigh moisture vapor transmission rates (MVTR) unless additional vaporbarrier layers are incorporated.

Accordingly, it would be desirable if there were available flooringsystems that produced relatively low sound reflection (e.g., less thanabout 13.5 dB average over a range of 300 to 1000 Hz) and moisture vaportransmission rates (e.g., less than about 3.0 lb/1000 ft²/24 hr) by ASTMF1249 test method, without the cost and installation complexityconventional systems typically involve.

SUMMARY OF THE INVENTION

A flooring system as disclosed herein may include an underlaymentmaterial that provides for low reflected sound pressure level (SPL) aswell as low moisture vapor transmission rate (MVTR). Such a flooringsystem may include a top floor layer, a sub-floor, and an underlaymentmaterial disposed between the sub-floor and the top floor layer.

The underlayment material may include a cross-linked, polyolefin foamhaving an MVTR of less than about 3.0 lb/1000 ft²/24 hr. The foam mayproduce an average reflected SPL of less than about 13.5 dB over a rangeof about 300 Hz to about 1000 Hz.

The foam may have a resin composition, foam density, and gel fractionthat, in combination, produce the average reflected sound pressure levelof less than about 13.5 dB. For example, the foam density may be atleast about 30 kg/m³ and the gel fraction may be at least about 40%. Inan example embodiment, the foam density may be between about 50 kg/m³and about 60 kg/m³, the gel fraction may be between about 50% and about60%, and the foam may have a thickness between about 1.5 mm and about2.5 mm. The foam may have a compressive strength of at least about 0.85kg/cm².

The resin composition may include an olefin homopolymer or copolymer,such as a blend of polyethylene and polypropylene copolymer, such asethylene propylene copolymer and linear low-density polyethylene. Theethylene propylene copolymer content may be at least 20% by weight. Thefoam may have a fine cell structure with cells having diameters betweenabout 0.1 millimeter and about 1 millimeter.

The underlayment material may include an additive, such as ananti-microbial additive, a flame retardant additive, or an adhesionpromoter. A vapor barrier layer may be disposed between the top floorlayer and the sub-floor. The foam may be laminated to another layer,which may include a non-woven, a film, and another foam. The foam may beembossed, textured, or molded.

The underlayment material may be lightweight, thereby making theinstallation of the underlayment material easy and convenient. Forexample, a 100 ft² roll of the underlayment material may weigh less thanabout 5 lbs. Thus, a polyolefin foam underlayment material may provide,in combination, low moisture vapor transmission rates (MVTR), lowreflected sound pressure levels (SPLs), and a light weight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example of a flooring system with an underlaymentmaterial that provides for low reflected sound pressure level (SPL) aswell as low moisture vapor transmission rate (MVTR).

FIGS. 2A and 2B depict cross-sectional views of flooring systems withunderlayment material layers that provide for low reflected SPL andMVTR.

FIG. 3 provides a graph of average reflected SPL as a function ofcompressive strength for each of a number of underlayment materials.

FIGS. 4A-4D provide graphs of average reflected SPL as a function offrequency for various foam underlayment materials.

FIG. 5 is a flowchart of a method for manufacturing a low reflected SPL,low MVTR, cross-linked, polyolefin foam underlayment material.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As shown in FIGS. 1 and 2A, an example flooring system 100 may include atop floor layer 102, a foam underlayment material 104, and a sub-floor106. The top floor layer may include, for example, a laminate orhardwood flooring material. The underlayment material 104, which isdescribed in detail herein, may be, for example, a foam underlaymentmaterial such as, the FloorMuffler™, which is manufactured by TorayPlastics (America), Inc. and distributed by Diversified Foam Products,Inc. (www.floormuffler.com). The sub-floor 106 may be a wood or concretesub-floor, for example. It should be understood that the sub-floor 106might be a previously-installed flooring system, for example, that is tobe covered over, or any support structure, such as a system of floorjoists, for example, on which the top layer 102 and underlaymentmaterial are installed to form a flooring system.

The layers 102, 104, and 106 may be affixed to one another by anypracticable means. For example, the layers 102, 104, and 106 may benailed or tacked together. Optionally, an adhesive 110 may be appliedbetween the top floor layer 102 and the underlayment material 104. Theadhesive 110 may be a high-performance wood adhesive, for example.Optionally, an adhesive 112 may be applied between the underlaymentmaterial 104 and the sub-floor 106. The adhesive 112 may be ahigh-performance underlayment adhesive, for example.

As shown in FIG. 2B, the flooring system may include an optional vaporbarrier layer 108. As described in detail herein, the underlaymentmaterial may have moisture vapor transmission properties that aresuitable for certain applications. In some applications, however,additional moisture vapor protection may be desirable. If desired, avapor barrier layer 108 may be disposed between the top floor layer 102and the sub-floor 106. The vapor barrier layer 108 may be a film, whichmay be a polypropylene film, disposed between the underlayment material106 and the sub-floor 104. The vapor barrier layer may be adhered to theunderlayment material and/or to the sub-floor. It should be understoodthat the vapor barrier layer may be adhered to the underlayment materialbefore it is rolled (as described below). Thus, the underlaymentmaterial may be delivered to the point of installation with the optionalvapor barrier already adhered thereto, thus simplifying installation ofthe underlayment and vapor barrier.

The underlayment material 104 may include a cross-linked polypropylenecopolymer (EPC) and a linear low density/polyethylene (LLDPE) blend foamwith an EPC content of about 20% to 90% by weight. Preferably, the EPCcontent is between 50% and 90%. More preferably, the EPC content isbetween 70% and 90%. Other olefin materials that are suitable for useinclude, for example, homopolymers and copolymers of polyethylene,including high-density polyethylene (HDPE), low-density polyethylene(LDPE), very-low-density polyethylene (VLDPE), ultra-low-densitypolyethylene (ULDPE), and polymers or copolymers of polypropylenes,including cross-linked ethylene propylene copolymer.

The underlayment material 104 may have a 25% compressive strength of atleast about 0.10 kg/cm², as measured by JIS K6767. Materials havingcompressive strength below about 0.85 kg/cm² tend to be too soft andproduce high reflected SPL. Preferably, the underlayment material 104has a 25% compressive strength of at least about 1.0 kg/cm². Morepreferably, the underlayment material 104 has a 25% compressive strengthof at least about 1.2 kg/cm².

FIG. 3 provides a graph of reflected sound pressure level, averaged overthe range of 300-1000 Hz, as a function of compressive strength for anumber of underlayment materials. As shown, foams with 25% compressivestrengths of at least about 0.85 kg/cm² tend to produce averagereflected sound pressure levels of less than about 13.5 dB. FIG. 3 alsoprovides data for underlayment materials used in prior art flooringsystems, with compressive strengths of less than about 0.85 kg/cm², thattend to produce average reflected sound pressure levels of more thanabout 13.5 dB.

Compressive strength is a property of the foam structure obtainedprimarily by the selection of resin, foam density, and the manufacturingprocesses used to convert resin into foam. It should be understood thathigher polypropylene content may produce higher compressive strengthand, accordingly, lower average reflected SPL. Density may also be afactor. For example, to increase compressive strength from approximately3 kg/cm² to approximately 6 kg/cm², the foam density might need to beincreased from about 100 kg/m³ to about 121 kg/m³.

FIG. 4A provides graphs of average reflected SPL as a function offrequency for various polypropylene content embodiments of a foamunderlayment material according to the invention. Average reflected SPLgraphs are provided for embodiments having polypropylene content ofabout: (1) 25 to 30%, (2) 50% to 60%, and (3) 70% to 90%.

The gel fraction (a.k.a., cross-link percentage or cross-link level) mayrange from about 15% to about 80%. Higher cross-link levels arepossible; however, if cross-linking is too high, the foam will bedifficult to roll onto a core, and will be difficult to lay flat makinginstallation difficult. A preferable range of cross-linking is 40% to60%, while the most preferable range is 50% to 60%. The type of resinsselected, the amount of chemical cross-linking agent used, and theamount of exposure to a radiation source such as an electron beamirradiation device determine the degree of cross-linking. Also, ingeneral, higher cross-link percentage provides slightly highercompressive strength. It is expected, therefore, that higher cross-linkpercentage should lead to slightly lower reflected SPL. It is alsoexpected that higher cross-link percentage should also lead to lowerMVTR.

FIG. 4B provides graphs of average reflected SPL as a function offrequency for various gel-fraction embodiments of a foam underlaymentmaterial according to the invention. Average reflected SPL graphs areprovided for embodiments having gel fractions of about: (1) 40%, (2)45%, (3) 50%, and (4) 55%.

The density of the underlayment, as determined by method ASTM D3575, maybe about 20 to 200 kg/m³. More preferably the density is 40 to 100kg/m³, while the most preferable range is 50 to 60 kg/m³. Foam densitiesof less than about 25 kg/m³ are possible; however, the underlayment maybe too soft and compress under loading. Higher density tends to increasethe compressive strength of the foam and thereby reduce the reflectedSPL. Increasing foam density, however, tends to add to product cost dueto increased raw material consumption to manufacture. For example, the25% compressive strength results (and associated reflected soundproperties) described above may result from formulating a cross-linkedpolyethylene, polyethylene blend, or other polymeric foam at higherdensities (such as 100 to 200 kg/m³), though it is expected that suchformulation may be cost prohibitive. Density may be controlled by anumber of factors, the types of resins used, the degree ofcross-linking, process conditions, and the type and amount of foamingagent used.

FIG. 4C provides graphs of average reflected SPL as a function offrequency for various density embodiments of a foam underlaymentmaterial according to the invention. Average reflected SPL graphs areprovided for embodiments having a density of about: (1) 56 kg/m³, (2) 40kg/m³, (3) 45 kg/m³, and (4) 50 kg/m³.

The thickness of the underlayment ranges from about 0.5 mm to about 6.0mm, most preferably from 1.5 to 2.5 mm. Thinner foams than 0.5 mm maylack the resiliency under the loading of the flooring system. Foamsthicker than about 6.0 millimeters are also suitable for underlaymentmembranes, however relatively thick layers of around 6.0 millimeters ormore may interfere with wall molding or door clearances. Thickness isdetermined by the resin selection, type and amount of chemical foamingagent used, extruded sheet thickness, tension during the foamingoperation, and the amount of heat applied during the conversion of sheetinto foam.

FIG. 4D provides graphs of average reflected SPL as a function offrequency for various thickness embodiments of a foam underlaymentmaterial according to the invention. Average reflected SPL graphs areprovided for embodiments having thicknesses of about: (1) 4.5 mm; (2)2.0 mm; and (3) 3.0 mm.

An underlayment material according to the present invention may providefor reduced MVTR, as well as improved reflected sound performance,without the need for the additional barrier layers, in a lightweight,easy-to-handle material. The current invention, with MVTR of <3.0lb/1000 ft²/24 hr, meets flooring industry standards for MVTR of lessthan 3.0 lb/1000 ft²/24 hr without the need for additional vapor barrierlayers that add to both product cost and weight. A 100 ft² roll of theunderlayment foam weights less than about 5 lbs, while providing lowreflected sound pressure levels in the 300 Hz to 1000 Hz range and MVTRperformance that meets flooring industry standards. This light weightallows easy transport and easy handling and positioning duringinstallation, with a minimum of manpower.

Example Methods for Manufacturing a Polyolefin Foam UnderlaymentMaterial

FIG. 5 provides a flowchart of an example method 200 for manufacturing apolyolefin foam underlayment material. At 202, one or more polyolefinresins may be mixed with a foaming agent, one or more cross-linkingagents, and/or one or more additives, into a homogenous mixture.Examples of polyolefin resins include polyethylene or polypropylene.Examples of cross-linking agents include peroxides (e.g., di cumylperoxide, etc.) for polyethylenes, and di vinyl benzene forpolypropylenes. Examples of additives include flame retardants, adhesionpromoters, colorants, and anti-microbial agents.

A homogenous mixture may be achieved by spinning the mixture in amechanical mixer designed for compounding plastic resins. Examples ofsuch mixers are well-known. To ensure complete and proper mixing,agitation rate, temperature, and processing duration may be selectivelycontrolled during this step by well-known industrial process controlmeans.

At 204, the mixture may charged, for example, into a conventionalplastics extruder, into which the ingredients are conveyed in a barrelby a screw, to produce a solid, thin, plastic web. The ingredients maybe initially compressed and mixed as the materials move along the screw.Heater elements, along with the shearing action of materials againsteach other and the screw and barrel, cause the resins to melt into aviscous liquid state. Additives and/or colorants may be added to theproduct at this stage of the process as well. The screw pushes themelted extrudate through a die opening to produce the thin, solid web.The web may typically be between about 0.2 and about 3.0 millimeters inthickness, although not limited, as thicker or thinner webs can beproduced as desired. As it is extruded, the web may cool from a moltenstate to a solid state. The web may then be trimmed, and wound into aroll.

At 206, the polymer resins may be cross-linked together. For example,irradiation of the polyolefin plastic can be done by electron beam.Other methods, such as chemical cross-linking, for example, may beemployed. The degree of cross-linking may be controlled to result in atypical cross-link density of about 15% to about 80%. A higherpercentage level of cross-linking is possible if desired. A desireddegree of cross-linking may be achieved by the type of resins selected,the amount of chemical cross-linking agent used, and the exposure to aradiation source such as an electron beam irradiation device.

At 208, the continuous polymer web may be converted into a low-densityfoam. For example, the foam may be heated by radiant heaters, moltensalt, hot air, or other heating devices. The heat causes a reaction ofthe chemical foaming agent that causes the foaming agent to releasesgases, thus forming a cellular structure in the web. The combination ofresins selected, cross-linking, and the process used may be selected tocreate a fine-celled structure, with typical cells ranging from about0.1 to about 1.0 millimeter. It should be understood that larger andsmaller cell sizes are possible.

A desired thickness may be achieved by the resin selection, type andamount of chemical foaming agent used, extruded sheet thickness, tensionduring the foaming operation, amount of heat applied during theconversion of sheet into foam. For example, an extruded sheet having athickness of about 1 millimeter may produce a relatively high densitypolyolefin foam having a thickness of about 1.5 millimeter if littlefoaming agent is used. A relatively low density foam having a thicknessof about 2.5 millimeter may be produced if a greater quantity of foamingagent is used.

A desired density may be achieved by the selection of resins used, thedegree of cross-linking, process conditions, and the type and amount offoaming agent used.

At 210, the finished foam web may be rolled onto a core, such as acardboard or paper tube, for example.

The foam web may undergo further processing at 212. For example, thefoam web may be coated with an adhesive layer or release layer,laminated with films, fabrics, nonwovens, or other foams, or molded forany of a variety of uses, such as automotive instrument panels, gaskets,or packaging, for example.

Reflected Sound Test

Reflected sound pressure levels were measured using a test methodloosely based on Association of European Producers of Laminate Flooringtest method EPLF NORM021029-1. The test method employed was a simplifiedversion of EPLF NORM01029-1 to compare relative differences in reflectedsound between different underlayment materials. The sound source for thetest was the tapping machine specified by ASTM E492 placed on the centerof the test specimen. The test specimen consisted of a 6′×6′ squaresample of the particular underlayment and laminate flooring centered ona 12′×16′×6″ concrete slab, which is specified for ASTM E492 testing.Three measuring microphones were placed in the same room as the tappingmachine to measure the sound produced by the tapping machine impactingthe floor sample. The microphones were placed 120 degrees apart, 1.5meters from the center of the floor sample. Third octave frequency bandmeasurements from 100 Hz to 10,000 Hz were taken for 15 seconds for eachof the three microphones. The average sound pressure levels were thencalculated for the 300 Hz to 1000 Hz range.

Determining the Percent of Polymer Cross-Linking Achieved by theIrradiation Process.

Apparatus used to determine the percent of polymer cross-linkingincluded: 100 mesh, 0.004″ wire diameter, type 304, stainless steelbaggies; numbered wires & clips; a Miyamoto thermostatic oil bathapparatus; an analytical balance; a fume hood; a gas burner; a hightemperature oven; an anti-static gun; and three 3.5 liter wide mouthstainless steel containers with lids. Reagents and materials usedincluded: a solvent, such as tetralin high molecular weight solvent,used to determine the gel fraction; acetone; and silicone oil.

An empty wire mesh bag was weighed and the weight recorded. For eachsample, about 2 grams to about 10 grams +/− about 5 milligrams of samplewas weighed out and transferred to the wire mesh bag. The weight of thewire mesh bag and the foam cutting was recorded in the Gel Fraction log.

Each bag was attached to the corresponding number wire & clips.Dissolving of non-crosslinked foam. When the solvent temperature reachesa target temperature, the bundle (bag and sample) was immersed in thesolvent. The samples were shaken up and down about 5 or 6 times toloosen any air bubbles and fully wet the samples. The samples wereattached to an agitator and agitated so that the solvent can dissolvethe foam. Oil bath apparatus was shut off The samples were then cooledin a fume hood.

The samples were washed by shaking up and down about 7 or 8 times in acontainer of primary acetone. The samples were washed a second time in asecond acetone wash. The washed samples were washed once more in a thirdcontainer of fresh acetone as above. The samples were hung in a fumehood to evaporate the acetone, about 1 to about 5 minutes.

The samples were dried in a drying oven for about 1 hour. The sampleswere cooled for a minimum of about 15 minutes. The wire mesh bag wasweighed on an analytical balance and the weight was recorded.

Gel fraction could then be calculated as Gel Fraction=100*(C −A)/(B−A),where A=empty wire mesh bag weight; B=wire bag wt+foam sample beforeimmersion in solvent; and C=wire bag wt+dissolved sample after immersionin solvent.

Thus, there have been described improved flooring systems having thatproduce relatively low sound reflection and moisture vapor transmissionrates. It should be understood that the specific embodiments describedherein are merely examples, and that the scope of the invention may bedetermined from the following claims. Specifically, it should beunderstood that the ranges provided for gel fraction, density,thickness, and polypropylene content, and the example combinationsthereof described herein, are examples. It is contemplated that manyother combinations of gel fraction, density, thickness, andpolypropylene content may produce foams having reflected sound andmoisture vapor barrier properties in accordance with the invention.

What is claimed:
 1. A floor system, comprising: a top layer; asub-floor; and an underlayment material comprising a cross-linked,polyolefin foam disposed between the sub-floor and the top layer,wherein the flooring system produces an average reflected sound pressurelevel of less than about 15dB over a range of about 300-1000Hz.
 2. Afloor system, comprising: a top layer; a sub-floor; and an underlaymentmaterial comprising a cross-linked, polyolefin foam disposed between thesub-floor and the top layer, wherein the cross-linked, polyolefin foamhas a Moisture Vapor Transmission Rate (MVTR) of about 0.3-2.0 lbs/1000ft²/24 hours, wherein the flooring system produces an average reflectedsound pressure level of less than about 15dB over a range of about300-1000 Hz.